Perovskite photovoltaics have shown great promise in device efficiency but also the promise of scalability through solution‐processed manufacture. Efforts to scale perovskites have been taken through printable mesoporous scaffolds and slot die coating of flexible substrates roll‐to‐roll (R2R). However, to date there has been no demonstration of entirely R2R‐coated devices due to the lack of a compatible solution‐processable back electrode; instead, high‐value evaporated metal contacts are employed as a post process. Here, in this study, the combination of a low‐temperature device structure and R2R‐compatible solution formulations is employed to make a fully R2R printable device architecture overcoming interlayer incompatibilities and recombination losses. Therefore, the n–i–p device structure of SnO₂/perovskite/poly(3,4‐ethylenedioxythiophene)/carbon is employed to form an ohmic contact between a p‐type semiconductor and printable carbon electrode. In particular, the results show that the small‐scale device efficiencies of 13–14% are achieved, matching the device performance of evaporated gold electrodes. Also, this entirely R2R‐coated perovskite prototype represents a game changer, reaching over 10% (10.8) stabilized power conversion efficiency with unencapsulated long‐term stability retaining 84% of its original efficiency over 1000 h under 70% RH and 25 °C.

Perovskite solar cells have emerged as a promising and highly efficient solar technology. Despite efficiencies continuing to climb, the prospect of industrial manufacture is in part hampered by concerns regarding the safety and sustainability of the solvents used in lab scale manufacture. In this paper, we aim to present a methodology for green solvent selection informed by EHS considerations from the CHEM-21 solvent guide for successful methylammonium lead triiodide (MAPbI₃) precursor dissolution. Through the use of this methodology we present a N,N-dimethylformamide (DMF)-free alternative solvent system for deposition of MAPbI₃ precursors (MAI and PbI₂) consisting of dimethyl sulfoxide (DMSO), dimethylpropyleneurea (DMPU), 2-methyltetrahydrofuran (2-MeTHF) and ethanol (EtOH). We have investigated 3 candidate solutions with slightly different compositions of these four solvents, all of which produce dense, uniform and pinhole-free perovskite films via spin coating. All three candidate solutions (A–C) match the average device efficiencies of the DMF/DMSO control devices (12.4%) with candidate A, which consists of 40% DMSO, 30% DMPU, 20% 2-MeTHF and 10% EtOH (vol%), producing a champion PCE of 16.1% compared to 16.2% for DMF/DMSO (80/20 vol%). Perovskite films cast from the three candidate solutions show improved crystallinity, higher fluorescence emission, and improved crystal size uniformity than those cast from DMF/DMSO. This work aims to: highlight the key solvent parameters which determine effective MAPbI₃ precursor dissolution; provide a set of criteria for appropriate alternative solvent selection; and demonstrate the application of green chemistry principles to solvent selection for perovskite photovoltaic manufacturing.

In this work, the effect of varying the size of the precursor raw materials SiO₂ and ZrO₂ in the solid-state synthesis of NASICON in the form Na₃Zr₂Si₂PO₁₂ was studied. Nanoscale and macro-scale precursor materials were selected for comparison purposes, and a range of sintering times were examined (10, 24 and 40 h) at a temperature of 1230 °C. Na₃Zr₂Si₂PO₁₂ pellets produced from nanopowder precursors were found to produce substantially higher ionic conductivities, with improved morphology and higher density than those produced from larger micron-scaled precursors. The nanoparticle precursors were shown to give a maximum ionic conductivity of 1.16 × 10⁻³ S cm⁻¹ when sintered at 1230 °C for 40 h, in the higher range of published solid-state Na₃Zr₂Si₂PO₁₂ conductivities. The macro-precursors gave lower ionic conductivity of 0.62 × 10⁻³ S cm⁻¹ under the same processing conditions. Most current authors do not quote or consider the precursor particle size for solid-state synthesis of Na₃Zr₂Si₂PO₁₂. This study shows the importance of precursor powder particle size in the microstructure and performance of Na₃Zr₂Si₂PO₁₂ during solid-state synthesis and offers a route to improved predictability and consistency of the manufacturing process.

Green solvent mixes are applied in printed mesoscopic perovskite solar cells and modules, achieving 13.8% PCE at 1 cm ² and >9% PCE in a 220 cm ² module. This shows how green solvent engineering can aid improvement and scale-up in emerging technologies.

The fully printable carbon triple-mesoscopic perovskite solar cell (C-PSC) has already demonstrated good efficiency and long-term stability, opening the possibility of lab-to-fab transition. Modules based on C-PSC architecture have been reported and, at present, are achieved through the accurate registration of each of the patterned layers using screen-printing. Modules based on this approach were reported with geometric fill factor (g-FF) as high as 70%. Another approach to create the interconnects, the so-called scribing method, was reported to achieve more than 90% g-FF for architectures based on evaporated metal contacts, i.e., without a carbon counter electrode. Here, for the first time, we adopt the scribing method to selectively remove materials within a C-PSC. This approach allowed a deep and selective scribe to open an aperture from the transparent electrode through all the layers, including the blocking layer, enabling a direct contact between the electrodes in the interconnects. In this work, a systematic study of the interconnection area between cells is discussed, showing the key role of the FTO/carbon contact. Furthermore, a module on 10 × 10 cm² substrate with the optimised design showing efficiency over 10% is also demonstrated.